Countdown timer: updating controller view labels - ios

Question

I am trying to set up a countdown timer. I have two view controllers: ViewController and EditViewController. ViewController has two labels hours and minutes. EditViewController has a UIDatePicker and a save button. When the user selects a time on the UIDatePicker and hits save, they are redirected back to the ViewController and the hour and minute labels are populated with the difference between the selected time and current time. This is automatically updated until the difference is 0. I have having issues trying to get the hour and minutes to display correctly on the ViewController labels. Here is my code:
ViewController.m
#interface ViewController ()
#end
#implementation ViewController
- (void)viewDidLoad
{
[super viewDidLoad];
// Do any additional setup after loading the view, typically from a nib.
self.hourLabel.text = self.hourText;
self.minuteLabel.text = self.minuteText;
}
- (void)didReceiveMemoryWarning
{
[super didReceiveMemoryWarning];
// Dispose of any resources that can be recreated.
}
#end
EditViewController.h
#interface EditViewController : UIViewController
#property (weak, nonatomic) IBOutlet UIDatePicker *datePicker;
#property (weak, nonatomic) IBOutlet NSString *currentTimeString;
#property (weak, nonatomic) IBOutlet NSString *endTimeString;
- (IBAction)saveButton:(id)sender;
- (IBAction)cancelButton:(id)sender;
-(void)updateTime;
#end
EditViewController.m
#import "EditViewController.h"
#import "ViewController.h"
#interface EditViewController ()
#end
#implementation EditViewController
- (id)initWithNibName:(NSString *)nibNameOrNil bundle:(NSBundle *)nibBundleOrNil
{
self = [super initWithNibName:nibNameOrNil bundle:nibBundleOrNil];
if (self)
{
// Custom initialization
}
return self;
}
- (void)viewDidLoad
{
[super viewDidLoad];
}
- (void)didReceiveMemoryWarning
{
[super didReceiveMemoryWarning];
// Dispose of any resources that can be recreated.
}
- (IBAction)saveButton:(id)sender
{
NSCalendar *now = [NSCalendar autoupdatingCurrentCalendar];
NSInteger currentTime = (NSHourCalendarUnit | NSSecondCalendarUnit);
self.datePicker.date = [now dateFromComponents:[now components:currentTime fromDate:self.datePicker.date]];
NSTimer *timer;
timer = [NSTimer scheduledTimerWithTimeInterval:1.0 target:self selector:#selector(updateTime) userInfo:nil repeats:YES];
[self dismissViewControllerAnimated:YES completion:nil];
}
-(void)updateTime
{
NSInteger timeLeft = ((NSInteger)[self.datePicker.date timeIntervalSinceNow]);
NSInteger minutes = (timeLeft / 60) % 60;
NSInteger hours = (timeLeft / 3600) % 24;
ViewController *controller;
controller.hourText = [NSString stringWithFormat:#"%ldi",(long)hours];
controller.minuteText = [NSString stringWithFormat:#"%ldi",(long)minutes];
NSLog(#"The time is %ld",(long)timeLeft);
}
- (IBAction)cancelButton:(id)sender
{
[self dismissViewControllerAnimated:YES completion:nil];
}
#end
Any help is appreciated. Thanks in advance.

Answer 1

Have a look at here for the edited method from your code. This will full-fill your requirement.
#import "EditViewController.h"
#import "ViewController.h"
#import "AppDelegate.h"
#interface EditViewController ()
{
AppDelegate *appDelegate;
}
#end
#implementation EditViewController
- (id)initWithNibName:(NSString *)nibNameOrNil bundle:(NSBundle *)nibBundleOrNil
{
self = [super initWithNibName:nibNameOrNil bundle:nibBundleOrNil];
if (self)
{
// Custom initialization
appDelegate = (AppDelegate *)[[UIApplication sharedApplication] delegate];
}
return self;
}
-(void)updateTime
{
NSInteger timeLeft = ((NSInteger)[self.datePicker.date timeIntervalSinceNow]);
NSInteger minutes = (timeLeft / 60) % 60;
NSInteger hours = (timeLeft / 3600) % 24;
NSString *hourText = [NSString stringWithFormat:#"%ldi",(long)hours];
NSString *minuteText = [NSString stringWithFormat:#"%ldi",(long)minutes];
[appDelegate updateTime:hourText andMinute:minuteText];
}
and finally, define a method in AppDelegate class
- (void) updateTime:(NSString *)hourStr andMinute:(NSString *)minuteStr
{
for(id obj in [self.navigationController viewControllers])
{
if([obj isKindOfClass:ViewController])
{
ViewController *vcObj = (ViewController *)obj;
vcObj.hourLabel.text = hourStr;
vcObj.minuteLabel.text = minuteStr;
}
}
}

Answer 2

Several issues:
ViewController.m
self.hourLabel.text = self.hourText;
self.minuteLabel.text = self.minuteText;
Should be in viewWillAppear instead of viewDidLoad. What's happening is you set the text when the app loads. viewDidLoad will only fire once for that instance of the app ever. What you're needing to do is update it when you come back from the EditViewController, right? So if you put it in viewWillAppear, it will also get called when you come back and update it for you.
The next thing:
EditViewController.m
ViewController *controller;
controller.hourText = [NSString stringWithFormat:#"%ldi",(long)hours];
controller.minuteText = [NSString stringWithFormat:#"%ldi",(long)minutes];
NSLog(#"The time is %ld",(long)timeLeft);
This code snippet is declaring a new ViewController variable (well, most of it, you're missing the = [ViewController new] part). The problem with this is that you don't do anything with this controller. ViewController is actually already in your navigation stack (I'm assuming NavigationController since you said when the user goes back), so you need to use the reference to ViewController your app has already instantiated, not create a new one since you never use this guy anywhere.